Carburetor for supercharged engine



Jan. 8, 1963 H MaolNNEs Y 3,072,389

CARBURETOR FOR SUPERCHARGED ENGINE Filed March 15, 1959 Unite tates Patent 3,072,339 CARBURETOR FR SUPERCHARGED ENGNE Hugh Macinnes, Richmond Heights, (Ehio, assignor to Thompson Ramo Wooldridge Inc., Cleveland, Ohio, a corporation of Ohio Filed Mar. 13, 1959, Ser. No. 799,320 1 Claim. (Cl. 261-30) The present invention relates to an improved mechanism for supercharging and supplying fuel to an internal combustion gasoline engine utilizing a naturally aspirated carburetor.

The present invention contemplates the provision of a supercharging air compressor for delivering pressurized air to an engine intake manifold. A naturally aspirated carburetor type of fuel supply means is connected to the intake of the air compressor. The fuel supply means will deliver fuel to the air compressor as a function of the air ow through the intake conduit, and embodies a venturi with a fuel supply orifice or jet opening into` the venturi. The venturi and jet are in the intake of the compressor, so that will not be subjected to the discharge pressure of the compressor. A throttle valve is positioned in the discharge conduit of the compressor for controlling the flow of air to the engine and is downstream of the air compressor so that the compressor Will not be subjected to the vacuum created by closing the throttle Valve at idle conditions. The throttle valve may be of the type having a plate mounted on the rotary shaft with the shaft provided with seals to prevent the leakage of air or of air-fuel mixture along the shaft. An idle fuel supplying means is connected to the air discharge conduit downstream of the throttle valve and includes an air bleed by-pass line connected upstream of the throttle valve'with an idle fuel orifice opening in the air bleed line, and with an air adjustment valve to control the idle fuel supply. A starting fuel enrichment arrangement may be provided such as in the form of -a choke valve upstream of the venturi -or of a separate enrichment jet downstream of the throttle valve.

An object of the present invention is to provide an improved mechanism for supply fuel and pressurized air to a supercharged gasoline engine which uses a naturally aspirated type of carburetor for the fuel supply and which overcomes the difficulties heretofore encountered due to the necessity of pressurizing of fuel conduits and fuel connections communicating with these conduits.

Another object of the invention is to provide an improved air-fuel system for an Otto-cycle internal combustion engine wherein the fuel supply is connected upstream of the compressor so as to avoid the necessity of pressurizing the fuel supply and the necessity of providing pressure seals for the fuel supply.

Another object of .the invention is to provide a supercharging system for an Otto-cycle gasoline engine using a naturally aspirated carburetor for the fuel supply system and wherein the throttle valve may be located downstream of the compressor so as to avoid the necessity of providing oil seals for preventing the leakage of oil from the compressor bearings into the compressor housing to mix with the air-fuel mixture.

Another object of the invention is to provide an improved combined naturally aspirated carburetor type of fuel supply system in combination with a supercharger for an `Otto-cycle internal combustion engine with an improved idle fuel supply arrangement.

A still further object of the invention is to provide an improved supercharged yfuel supply system for an Ottocycle internal combustion gasoline engine with an improved fuel supply arrangement for cold starting conditions.

Other objects and advantages will become more appar- 3,072,389 Patented Jan. 8, 1963 ice ent with the disclosure of the preferred embodiment of the invention in the specification, claim and drawings, in which:

FIGURE l is a front elevational view with parts broken away illustrating a mechanism for supercharging and supplying fuel to an engine and embodying' the principles of the present invention;

FIGURE 2 is a vertical sectional view rtaken substantially along line Il-II of FIGURE l, and illustrating details of the internal construction of the mechanism of FIGURE l; and,

FIGURE 3 is a vertical sectional view similar to FIG- URE 2, and illustrating a modified form of the invention.

As shown on the drawings:

The mechanism illustrated in the drawings embodying the preferred forms of the present invention is utilized for supercharging and supplying fuel to a gasoline-fueled Otto-cycle internal combustion engine. A compressor 6 is provided for compressing the air supplied to the engine, and in the present form, compresses an air-fuel mixture.

Ynot shown.

The compressor chamber 8 discharges compressed airfuel mixture through an air discharge conduit 11 and the conduit is provided with a housing'llange 7a for connection to another conduit leading directly to the intake manifold of the engine. f

The air-fuel mixture which `is compressed by the compressor 6 is taken in through an air intake conduit 12 which is formed by a central hub 7b of the compressor housing.

The air intake conduit has a Venturi portion 13 into which the fuel is supplied to mix with the incoming air. For this purpose, an orifice or jet 16 opens into the venturi portion 13 and fuel is supplied at the orifice througha fuel line 17, leading from a float chamber 18 supplied with fuel from a pump 19, which draws fuel from a fuel line 2,1. This fuel supply arrangement offers a preferred form of supplying fuel to be mixed With the air entering the compressor with the fuel supply varying as a function of the ow of air through the air intake conduit. Inasmuch as the fuel supply is upstream of the compressor, the fuel supply elements Will not be subjected to pressures greater than atmospheric, and, there.- fore, the fuel supply need not be pressurized, and the line and fittings need not be provided with pressure seals, as is the case when the fuel must be supplied downstream of the compressor.

For purposes ofenriching the air-fuel mixture during cold starting periods, a choke valve 22 is provided in an enlarged passageway 14 upstream of the venturi portion 13 formed by ared out section 7c of the housing. The choke valve 22 is shown in the cold starting position when the flow of air through the venturi is restricted to increase the flow of fuel in a well-known manner. The choke valve 22 is shown in broken lines in the position in which it will be placed during normal operation of the engine and of the fuel supply mechanism.

In the air discharge conduit 11 defined by the housing -wall 7d and downstream from the compressor, is a throttle valve 23. In the embodiment illustrated, the throttle valve includes a llat throttle plate 24 secured to a rotary throttle shaft 26 which extends through the housing wall 7d. Seals Z7 and 28 are provided to seal the shaft 26 at the locations where it passes through the walls 7d to prevent the escape of air-fuel mixture from the conduit 11 during normal operation, and the seals also prevent the flow of air along the shaft during idling conditions.

As will be recognized, the area 25 downstream of the throttle valve will be under pressure during normal supercharged operation when the throttle valve is in the solid line position of FGURE 1. When the throttle valve is moved to the closed position (the solid line position of FIGURE 1), the area 25 will be subjected to vacuum from the intake manifold of the engine. Inasmuch as the .throttle valve is located downstream of the compressor 6, the compressor bearings are not subjected to the vacuum, and the bearings supporting the drive shaft 10 .need not be provided with special oil seals to withstand the high vacuum, and the problem of lubricating oil mixing with the air-fuel mixture in the compressor, and the problem of drawing oil from the bearings is not encountered.

In order to make possible the arrangement wherein the fuel supply need not be pressurized, and the compressor bearings need not be subjected to vacuum, and yet provide satisfactory idling of the engine, a separate idle fuel supply is provided. The idle fuel opens into the air discharge line 11 downstream from the throttle valve at 33. The idle fuel is supplied through an idle fuel orifice 34 supplied by an idle fuel line 36, leading to a suitable fuel supply, not shown. The idle fuel orifice 34 opens into an air bleed line 31, which connects at 32 to the air discharge conduit 11 upstream of the throttle valve 34, and connects to the air discharge line 11 downstream of the throttle valve 24 at 33. This provides a flow of air to aspirate idle fuel from the idle fuel line 36. The flow of idle air to control the idle fuel supplied is regulated by an adjustable needle valve 37, which is threaded into the by-pass line 31.

Thus fuel will be drawn from the idle fuel line when the throttle valve is closed. A check valve 30 is positioned in the fuel line 36 to prevent a flow of air into the line when the throttle valve is open.

While choking of the engine normally consumes a very short period of time, it is usually done at slow cranking speeds, and not at excessive vacuums, and the closing of the choke valve 22 will create a suction in the compressor housing 7. In some instances, this may be undesirable, and is avoided in the modified form illustrated in FIG- URE 3.

In this form, the same arrangement for carbureting the main fuel supply and idle fuel supply is used, but a starting enrichment line 39 is connected to the air discharge conduit 11 downstream of the throttle valve 23. In the arrangement illustrated, the line 39 is connected to an air-fuel flow conduit 38 which may be part of the intake manifold of the engine. Fuel is supplied to the starting enrichment line 39 through a fuel line 41, and the iiow is controlled by a valve 42 which may be thermostatically actuated by a control line 43 connected to the exhaust conduit or another part of the engine to operate the valve 42 as a function of engine temperature and supply additional fuel to enrich the air-fuel mixture during cold engine starting and running conditions.

In operation, as illustrated particularly in FIGURES l and 2, a compressor 6 is driven by the drive shaft 10 to compress the air-fuel mixture entering through the air intake conduit 12. Fuel is supplied through the fuel orifice 16 leading into the venturi portion 13. The throttle valve 23 is open during normal running, and is located somewhere between the dotted and solid line positions of the valve plate 24, as illustrated in FIGURE 1. At idle, the valve plate 24 is in closed idle solid line position in FIGURE 1 and air drawn through the idle bypass line 31 aspirates idle fuel through the orifice 34 and the fuel enters the air discharge conduit 11 downstream of the throttle valve 23.

It will thus be seen that I have provided a carburetor arrangement which is naturally aspirated, and utilized with a supercharging system, and which prevents the problems of change in air pressure in the air-fuel flow lines, which were heretofore encountered, and which meets the objectives and advantages hereinbefore set forth. The fuel supply system need not be pressurized, and thc provision of seals is avoided. Furthermore, the problems of leakage of oil from the parts of the compressor has been avoided. The mechanism may be constructed as a unit with the ange 7a adapted for direct connection on the intake manifold of an engine in place of the carburetor for conversion of an engine to a supercharged unit.

l have, in the drawings and specification, presented a detailed disclosure of the preferred embodiment of my invention, and it is to be understood that I do not intend to limit the invention to the specific forms disclosed, but intend to cover all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by my invention.

I claim as my invention:

A fuel and air supply mechanism for a supercharged internal combustion engine comprising in combination a rotary centrifugal air compressor having an axial air inlet conduit and having a tangential air discharge conduit, means for driving the rotary air compressor to compress air for supercharging an engine, a fuel supply conduit means connected to the air intake conduit and including a venturi portion and an enlarged portion upstream from said venturi portion, means defining a fuel supply jet opening into said venturi portion, a fuel supply conduit connected to said fuel supply jet, a choke valve connected in said enlarged portion, an air-fuel conduit connected downstream of said air compressor discharge conduit, a butterliy throttle valve in said air-fuel conduit including a valve plate mounted in the air-fuel conduit and a supporting pivotal shaft extending into the conduit through the walls of the conduit and connected to the plate, means between the wall of the air-fuel conduit and the shaft sealing the shaft and preventing the leakage of the air along the shaft, a by-pass air bleed passageway connected to said air-fuel conduit upstream of the throttle valve and downstream of the throttle valve, an idle oritice means opening into said air bleed line, an idle fuel conduit connected to said orifice, a reverse flow preventing check valve in said idle fuel conduit, and an air adjustment valve connected in said air bleed line upstream of said idle orifice to regulate the quantities of idle fuel supplied to the air-fuel conduit when the throttle valve is closed.

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